nfs: add cache_validity to the nfs_inode_event tracepoints

Managing the cache_validity flags is the deep voodoo of NFS cache
coherency. Let's have a little extra visibility into that value via the
nfs_inode_event tracepoints.

Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20250618-nfs-tracepoints-v2-1-540c9fb48da2@kernel.org


Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>